The Ethernet protocol has long been employed to implement computer networks wherein multiple computing devices (comprising for example computers, printers, scanners, etc.) are coupled together. In an Ethernet network, any device can exchange traffic with any other device via the transmission medium, which is typically the Ethernet cabling medium.
To facilitate discussion, FIG. 1 shows a segment of a typical Ethernet network, comprising four computers 102, 104, 106, and 108 all coupled to communicate via an Ethernet cable 110. If multiple devices attempt to communicate simultaneously on the same Ethernet cable 110, traffic collision occurs. To solve the traffic collision problem, Ethernet networks typically employ CSMA/CD (Carrier Sense Multiple Access/Collision Detection), which is a protocol for determining how network devices handle traffic collision. Generally speaking, CSMA/CD requires a network device to monitor the traffic on the transmission medium and transmit if there is no traffic on the transmission medium. If multiple devices attempt to transmit simultaneously, a collision occurs and is detected by all monitoring network devices. A network device thwarted by a network collision will set a random timer, and will attempt to transmit again when the timer expires. If another collision occurs, the random time interval is increased, and a longer time period would pass before that network device would attempt to transmit again. The exponential back off occurs until the network device is able to transmit its messages. CSMA/CD is well-known and is well documented in standards such as IEEE 802.3 and ISO 8802.3.
When one of the computers on an Ethernet network is infected with a virus, the virus may cause the infected computer to send out a large volume of packets, such as email packets, on the Ethernet network. The massive volume of data transmission by the infected computer in effect shuts down the network since no other network device may be able to employ the transmission medium for data transmission. By way of example, a network device adhering to the CSMA/CD will keep increasing its random wait time interval each time it attempts to transmit and fails. After some time, the network essentially bogs down.